As a signal feature extraction technique for analyzing features of an acoustic signal, a biological signal, or the like, there is analysis by a filter bank composed of a group of band-pass filters having different center frequencies and band widths (for example, see non-patent literature 1).
FIG. 1 schematically illustrates a processing flow of the filter bank. Here, a filter bank that applies three band-pass filters 1-3 to an input signal x(n) is considered. It is assumed that the filter bank is designed to match a specific input signal pattern to an impulse response of a specific band-pass filter. In an example of FIG. 1, a waveform pattern of the input signal x(n) is substantially the same shape as an impulse response h2(n) of the band-pass filter 2, and it is expected that only an output signal y2(n) of the band-pass filter 2 takes a large output value in response to the waveform pattern of the input signal x(n) compared among the output of the band-pass filters 1-3.